There are known many different ways for securing a cutting insert to an insert pocket of a cutting tool. For example, there are many known clamping mechanisms for clamping the cutting insert in the insert pocket that include a clamping screw. The clamping screw is inserted through a through-bore formed in the cutting insert, and screwably received in a threaded bore formed in the insert pocket, to clamp the cutting insert therein. In some cutting tools the clamping arrangement is ‘radial’, i.e., the rotation axis of the clamping screw is generally perpendicular to a radial plane—which is parallel to, and which extends through—the axis of rotation of the cutting tool.
In many metal cutting operations and specifically, in metal cutting operations involving high speed milling or in other intensive cutting operations, the clamping screw may be exposed to large forces. These forces may include, for example, centrifugal forces caused by the rotation of the cutting tool, forcing the cutting insert away from the insert pocket in a radially outward direction. Other large forces may include forces that arise from the interaction of the cutting insert with the work-piece, which might displace the cutting insert from its secured position in the insert pocket.
These large forces, especially if exerted for extended periods of time, risk deforming and eventually breaking the clamping screw, e.g., by tearing the screw-head away from the clamping screw body, or by breaking the clamping screw body in two—and thereby separating the cutting insert from the insert pocket. In attempt to prevent this, for example, some rotary cutting tools are deliberately limited to a relatively low rotation rate, which may lead to a limited performance of the cutting tools.
An additional disadvantage arises in some clamping mechanisms, in which the threaded bore and through-bore are manufactured to be eccentric to one another in order to force the cutting insert against supporting surfaces of the insert pocket upon fastening of the clamping screw. In some cutting tools using these clamping mechanisms, the eccentricity of the through-bore and threaded bore leads to unnecessary exertion of pressure on various parts of the clamping screw, thus weakening the clamping screw and decreasing the amount of externally exerted force that the clamping screw can withstand.
Attempts have been made to solve some of the above disadvantages. For example, some cutting tools are manufactured in which engagement of the bottom surface of the cutting insert with the corresponding attachment surface of the insert pocket is obtained by means of complementary elements formed in the two surfaces. Examples of such complementary elements are rib-groove elements, male like-female like elements, serrated elements, etc. The engagement obtained this way may relatively efficiently prevent undesired displacement of the cutting insert relative to the insert pocket during the cutting operation.
However, in cutting tools using the above-mentioned solution the engagement obtained between the surfaces extends over a plurality of large engagement areas. This may require extensive grinding and finishing of both the bottom and attachment surfaces, in order to obtain good engagement therebetween, and in addition to obtain an accurate placement of the cutting insert in the insert pocket. Therefore, some cutting tools that include these engagement means are expensive to manufacture, while in some others the cutting inserts are poorly positioned in their respective insert pockets.